Although examples of renewable energy include solar power generation, its penetration rate is still low. It is effective for a further widespread use of solar power generation to achieve high efficiency and low cost. As solar cells having been currently put to practical use, there have been known single-crystal Si, polycrystalline Si, amorphous Si, CIGS, and CdTe. However, since any of the solar cells are of a unijunction type, a theoretical upper limit of the efficiency is up to 30%.
As a candidate of a future solar cell capable of simultaneously realizing the high efficiency and the low cost, a light concentrating-type solar cell has been proposed. The light concentrating-type solar cell has an advantageous in terms of high efficiency and in that a panel area can be reduced for light concentrate. However, as disadvantages of the light concentrating-type solar cell, since a lens and a reflecting mirror are used for light concentrate, a structure of a light concentrator is complicate, heavy, and large, and in addition, a sunlight tracking device is required; therefore, contrary to expectations, there is a problem that the power generation cost is extremely high at present.